Transfer sheets for forming thermosensitive copies



y 10, 1960 F. G. FRANCIS ETAL 2,936,247

TRANSFER SHEETS FOR FORMING THERMOSENSITIVE COPIES Filed June 5, 1958 Coloured bans/er sbee/ male/7'01 Ped, blue or olber coloured lra/zsfemble coal/21g on base web.

Base

web.

[mpress/bns 0/ e bea s on base web.

Peel blue or olber coloured wr/llen cbaraclers on copy sbeel.

C sbeel lbe mall r on wb/cb Can b qaiea' by means of a l/lermo-sens/five topy/hg process.

TRANSFER SHEETS FGR FURMING THERMO- SENSITIVE COPIES (Md Southgate, London, and Seaward, Enfield, England, assiguors to Limited, London, England, a liritish coni- Frederick George Francis,

John Albert Carihonum P y The present invention relates to carbon paper and transfer sheet materials generally and is concerned in particular with carbon papers which are coloured, i.e. other than black.

Copying processes are known which make use of thermosensitive paper or other sheet material. In such processes, a sheet of thermo-sensitive material, such as a sheet of paper coated with one or more layers of a thermo-sensitive composition which produces a distinctive colouration in those areas subjected to a suitable increase in temperature, is placed in contact with and above the typewritten or other material to be copied and the sheets are then irradiated with infra-red rays. This generates a heat pattern in the copy sheets in accordance with the characters or other markings on the material to be copied and this heat pattern develops the copy sheet by producing the colouration in the thermo-sensitive composition thereof to produce a copy of the original material. In general, the infra-red rays are directed on to the material to be copied through the copy sheet, which is not itself absorbent of infra-red radiation.

It has been found that, generally speaking, satisfactory copies can be obtained by such processes only from black writings, such as duplicates made using black carbon paper, and that it is virtually impossible to operate a thermo-Sensitive copying process with coloured material. This method of copying is therefore not normally feasible with typewritten or other duplicates which are made with a coloured, e.g. red carbon paper. Good copies can be obtained from typed duplicates produced by means of a black carbon paper, which almost invariably carries a transfer composition which contains carbon black. Red carbon papers and other coloured transfer sheet material, such as purple, green and blue, are almost completely unsatisfactory from the standpoint of obtaining copies by means of thermo-sensitive copying paper from duplicates made by using them. Depending upon the colouring material used, brown carbon papers will sometimes produce matter which can be copied in this way, particularly if the brown colouring material in the transfer composition is obtained by the addition of carbon black to another colouring matter, such as a red pigment.

If graphite is added to the coloured pigmentary matter used in the manufacture of transfer compositions, in an attempt to overcome this defect of coloured material, small quantities of graphite are not particularly efiective, presumably because small quantities do not cause a sufiicient increase in the infra-red absorbative properties of the Whole mixture, while the addition of high proportions of graphite are also unsatisfactory because of their dulling effect on the written matter for ordinary purposes.

It is therefore an object of the present invention to provide a carbon paper or other transfer sheet material carrying a coloured, i.e. non-black, transfer composition which overcomes the defects of ordinary colouring materials in respect of thermo-sensitive copying processes.

According to the invention, a coloured carbon paper or other coloured transfer sheet material which is adapted atent O to produce coloured written copy matter capable of being copied by a thermo-sensitive copying process is provided, which comprises a paper web carrying a transferable coating which comprises at least one coloured material and graphite for rendering the coloured Written copy matter suificiently heat-absorbative to produce a heat pattern in a thermo-sensitive copy sheet when the latter is exposed to a source of heat when in contact with the coloured written copy matter, the graphite being present in an amount of up to 20% by Weight of the transferable coating, the colour of which is that due to the coloured material.

in the accompanying drawing, the single figure illustrates in fragmentary perspective transfer sheet material according to the invention.

it has been found that fairly large quantities of graphite within the stated range are generally required to give satisfactory results, namely between 15 and 20% by weight, but the colour of the other pigmentary or colouring matter used in the colouring material is not adversely affected to any appreciable extent and good results can be obtained in producing written matter by using the carbon paper. It has also been found that if the pro portion is increased beyond 20% by weight, the aforementioned disadvantage becomes apparent and, although duplicates made by using the carbon paper give good copies on thermo-sensitive paper, they are too dull in character and thereby give an extremely poor character to the writing, e.g. reds are turned into browns, and blues are turned into blue-blacks.

In order that the invention may be readily understood, the following specific examples are given.

Example 1.-F0r making red carbon paper sensitive to 1 Blue resinate consists of one part of Victoria Blue B Base (the base of Victoria Blue B, Colour Index N o. 729) mixed and milled on a hot threeroll mill with two parts of rosin.

We claim:

1. Red transfer sheet material which is adapted to produce red written copy matter capable of being copied by a thermo-sensitive copying process, which comprises a paper web carrying a transferable coating which comprises 12.2 parts by weight of fatty grey carnauba wax, 11.9 parts by weight of ceresine wax, 30.7 parts by weight of mineral oil and 27.7 parts by weight of Strong Red Lake, the transferable coating also including 17.5 parts by weight of graphite for rendering the red written copy matter sufficiently heat-absorptive to produce a heat pattern in a thermo-sensitive copy sheet when the latter is irradiated with infra-red radiation when in contact with the red written copy matter.

2. Blue transfer sheet material which is adapted to produce blue written copy matter capable of being copied by a thermo-sensitive copying process, which comprises a paper web carrying a transferable coating which comprises 19.75 parts by weightof fatty grey carnauba wax, 1750 parts by weight of petroleum jelly, 9.83 parts by weight of mineral oil, 7.33 parts by weight of Blue Resinate, 16.17 parts by weight of Strong Blue Lake, 15.16 parts by weight of Ultramarine Blue and 14.26 parts by weight of china clay, the transferable coating also includ- 4 ing 22.00 parts by weight of graphite for rendering the blue written copy mater sufficiently heat-absorptive to produce a heat pattern'in a thermo-sensitive copy sheet when the latter is irradiated with infra-red radiation in contact with the blue written copy matter.

References Cited in the file of this patent UNITED STATES PATENTS 

1. RED TRANSFER SHEET MATERIAL WHICH IS ADAPTED TO PRODUCE RED WRITTEN COPY MATTER CAPABLE OF BEING COPIED BY A THERMO-SENSITIVE COPYING PROCESS, WHICH COMPRISES A PAPER WEB CARRYING A TRANSFERABLE COATING WHICH COMPRISES 12.2 PARTS BY WEIGHT OF FATTY GREY CARNAUBA WAX11.9 PARTS BY WEIGHT OF FATTY GREY CARNAUBA WAX, OF MINERAL OIL AND 27.7 PARTS BY WEIGHT OF STRONG RED LAKE, THE TRANSFERABLE COATING ALSO INCLUDING 17.5 PARTS BY WEIGHT OF GRAPHITE FOR RENDERING THE RED WRITTEN COPY MATTER SUFFICIENTLY HEAT-ABSORPTIVE TO PRODUCE A HEAT PATTERN IN A THERMO-SENSITIVE COPY SHEET WHEN THE LATTER IS IRRADIATED WITH INFRA-RED RADIATION WHEN IS CONTACT WITH THE RED WRITTEN COPY MATTER. 